Expression of MMP1 and TIMP1 in radiation-combined wound healing and their effects on the healing process and tissue remodeling / 军事医学科学院院刊

ABSTRACT

Objective:To study the expression of MMP1 and TIMP1 in simple and radiation-combined wound healing and their effects on the healing process and tissue remodeling. Methods: A rat model of radiation-combined wound healing was used. Immunohistochemistry and in situ hybridization were performed which enabled the detection of MMP1 and TIMP1 expression in the healing process. Ultrastructural changes were observed with transmission EM. Results: The wound healing process was impaired and delayed. In rats receiving 25 Gy of gamma ray locally the irradiated wounds healed 6 days later than non-irradiated controls. The following changes in MMP1 and TIMP1 expression were found (1) In the early inflammatory phase and in the period of granulation tissue formation, MMP1 expression in the newly-formed epidermis of irradiated wounds approximated that in the controls. Later, the epidermal expression of MMP1 in radiation wounds was comparatively increased with the delay of the healing process.On days 3 to 14 after wounding, TIMP1 was weakly positive in the proliferating keratinocytes of control wounds and became negative after epidermal covering, whereas no or only slight epidermal expression was detected in radiation wounds before epidermal covering.(2)MMP1 and TIMP　1 expression in radiation wounds was markedlydecreased in fibroblasts　, endotheliocytes and macrophages as compared with the controls. The expression phase was prolonged due to the delay of the healing process.Conclusions:The reduced expression of MMP1 and TIMP1 in granulation tissue retards such important processes as cell migration, angiogenesis and tissue remodeling, thus retarding the healing process. The expression of MMP1 in the newly-formed epidermis may help the process of reepithelialization,but in the late healing period, overexpression of MMP1 and decreased expression of TIMP1 in the epidermis may hinder the establishment of basal membrane and the formation of granulation tissue, and thus affect the matrix remodeling process.